Bms 503 - Bacterial Growth and Growth Control

B period, C period, and D period

What are the three stages of the microbial cell cycle?

cell increases in mass and size until it reaches a certain mass which causes the beginning of C period

What occurs during B period?

the chromosome replicates and the two strands are segragated (separated)

What occurs during C period?

synthesis of a septum forms two identical cells

What occurs during D period?

20 minutes

How long does it take E. coli to complete the microbial cell cycle?

generation of ATP (chemo and phototrophs), generating lipids, amino acids, nucleotides, and cell walls, transcribing and translating proteins (structural or enzymatic)

What is happening during B period to make the cells get bigger?

at the division plane

Where is the cell wall produced during microbial cell cycle for cocci?

new peptidoglycan is inserted not only at divison sites but also along sidewalls during cell elongation (not poles)

Where is the cell wall produced in rod cells during microbial cell cycle?

dynamic and multifaceted

Prokaryotes contain a cell cytoskeleton that is what?

major shape-determining factor in prokaryotes

What is MreB?

forms spiral shaped bands around the inside of the cell under the cytoplasmic membrane, localizes synthesis fo new peptidoglycan and other cell wall componentsto specific locations during growth for rod bacteria (not in cocci)

What does MreB do?

sever pre-exisiting peptidoglycan creating breaks in the sugar backbone and peptide crosslinks

What do autolysins do?

a new unit of peptidoglycan is moved acorss the membrane to site of the lesion (unit = NAG linked to NAM with a peptide and the linked to bactoprenol)

What happens after the autolysins sever the peptidoglycan?

hydrophobic alcohol that carries NAG-NAM-peptide acorss the membrane

What is bactoprenol?

enzymes that interact with bactoprenol, insert cell was precursors into growing points of the wall, and catalyze glycosidic (NAG to NAM) bond formation

What are transglycosylases?

enzymes that form the peptide crosslinks between adjacent glycan chains (PBPs for short)

What are transpeptidases?

this is unique to prokaryotes, antibiotics target several steps in the biosynthesis, growing antibiotic resistance will require new drugs that target this pathway in different ways

Why is it important to care about the cell cycle?

E. coli can start a new round of DNA replication before it finishes the original round of DNA replication (4 generated cells vs 2)

A chromosome takes 40 minutes to replicate in E. coli, so why can their cell cycle take 20 min?

cell division following enlargement of a cell to twice its minimum size and the completion of one chromosome replication event

What is binary fission?

one cell gives rise to two cells

Binary =

splitting of one cell to two cells

Fission =

filamentous temperature-sensitive proteins

What are fts proteins?

interact to form the divisome (cell division apparatus), essential for cell division in all prokaryotes

What do the fts proteins do?

FtsZ forms ring around center of cell, ZipA anchor connects FtsZ ring to cytoplasmic membrane, FtsA connects FtsZ ring to membrane and recruits other divisome proteins

What are the steps to forming the divisome?

before (daughter chromosomes are yet to be formed)

DNA is replicated _____ the FtsZ ring forms

Min proteins

What is the location of the FtsZ ring facilitated by?

MinCD is a protein complex that oscillates from side to side, MinE follows MinCD causing it to fall apart, wherever MinCD and MinE are, FtsZ can't form a ring

What are the steps for determining the location of FtsZ by Min proteins?

poles (FtsZ forms ring in middle of cell)

As the cell gets longer and longer, MinCD and MinE spend most of their time at the ____

contracts

The FtsZ ring does what to divide the mother cell into two daughter cells?

interacts with the chromosome and prevents FtsZ from contracting before daughter chromosomes are segregated to each daughter cell

What does SlmA protein do?

exponential

Bacteria multiple asexually in an _____ fashion

genus and species, nutritional components of media, temperature of growth media, stress (chemicals, changing temp, pH changes)

The generation time is subject to what?

making quick estimates about doubling times

What are logarithmic growth graphs good for?

Nt = N0 + 2^n

What equation can you use to count final bacteria when you have the starting bacteria and the number of generations?

log10(Nt/N0) / 0.301 = n

What equation can you use to find out how many generations were made with the starting bacteria and total bacteria?

growth rate constant (k)

The number of generations (n) per unit time (t) is called what?

k=log10(Nt/N0) / 0.301t

What equation can you use to find the growth rate constant (k) with the time, total bacteria, and starting bacteria?

g=1/k

How can you calculate your mean generation time (g) from the growth rate constant (k)?

g=t/n

How can you calculate the generation time (g) from the time (t) and number of generations (n)?

closed-system microbial culture of fixed volume

What is a batch culture?

lag phase, exponential phase, stationary phase, death phase

What are the four phases of microbial growth?

interval between inoculation of a culture and beginning of growth, no cell division occurs while bacteria adapt to their new environment

What is lag phase?

when exponential grwoth of the population occurs, cells are healthiest

What is exponential phase?

population growth is limited, metabolism continues but at reduced rate, population is stagnant

What is stationary phase?

exhaustion of nutrients, accumulation of inhibitory metabolites or end products, exhaustion of space

What three things limit population growth in the stationary phase?

false - it cannot be determined because the population has stopped growing and dividing

T/F - when viable cells are being counted in stationary phase, it is determinable which cells are dying, dividing, and what the population is doing

the accumulation of waste products and scarcity of resources causes the population to decline in number (cells die but not all lose ability to divide)

What is the death phase?

subculture

What is it called when still viable cells of death phase get transferred to a new media to make new colonies?

growth conditions are constantly changing - impossible to independetly control both growth parameters

What occurs in batch culture?

low nutrient concentrations

Only during what conditions can both growth rate and growth yeild be controlled?

biomass/biomaterial created in culture

What is growth yield?

open-system microbial culture of fixed volume

What is a continuous culture?

most common type of continuous culture dvice where both growth rate and population density of culture can be controlled independently by manipulating dilution rate and concentration of limiting nutrient

What is a chemostat?

rate at which fresh medium is pumped in and spent medium is pumped out

What is dilution rate?

true

T/F - chemostat cultures are sensitive to the dilution rate and limiting nutrient concentration

the dilution rate (too high = washed away, too low = starvation)

The growth rate is controlled by what?

concentration of the limiting nutrient (no increasing volume, just concentration of nutrient medium)

The growth yield is controlled by what?

greater, same

Increasing concentration of a limiting nutrient results in _____ biomass but _____ growth rate

is allows for a scientist to keep a culture in exponential phase for longer periods than batch culture, generating larger amounts of total biomass/biomaterial

Why is continuous culture used?